The Latvian State Police said they had detained the 24-year-old suspect as he was about to board a minibus that would take him to the United Kingdom.
The first suspect, a 22-year-old man, was detained on Wednesday. A criminal probe has been launched over hooliganism.
But beyond the act of wanton destruction, questions are being asked about the people behind the exhibition, most prominently the photographer, US citizen Sergey Melnikoff.
Despite describing himself as a world-famous photographer, no professional photographers LSM spoke to had ever heard of Melnikoff except in connection with the recent controversy.
For a world-famous photographer, the images on Melnikoff's own website seem unexceptional and the site exhibits surprisingly rudimentary design work.
In contrast his claimed CV is extraordinary, giving an impression of a man who mixes with presidents, royalty and even the Dalai Lama as part of a jet-setting lifestyle.
However his actual links with the rich and famous seem more tenuous - as in the case of Queen Elizabeth II to whom he sent a picture (unsolicited) along with a request that she knight a friend of his.
Melnikoff also claims tohave three degrees including a PhD and be a Pulitzer Prize nominee from 2008, but a search of the Pulitzer database reveals no-one of the name Melnikoff and three with the first name Sergey, none of them photographers.
However, that just means Melnikoff was never a Pulitzer finalist. Anyone can be 'nominated' if they are prepared to pay a $50 entry fee and fill in some forms.
It seems a plan to establish a World Center for Photographic Art in a Saxon castle in Gorlitz, Germany didn't pan out as the town's official tourist site makes no mention of such a center.
But quite apart from his bona fides and debatable ability as a photographer - which seems to rely on the fact he possesses an ultra-high resolution camera that he says was a gift from Japanese manufacturer Fuji - a more serious question concerns whether Latvia should be seen to promote a man with some views that seem contrary to many basic European Union principles.
A Russian-language website linked to Melnikoff and which gives prominent coverage to the exhibition suggests forced deportation in cattle trucks of the Baltic Russian population, eugenics programs and assorted other horrors including a restoration of the Gulag system for a "degenerate" Russian population. (Readers are warned not to scroll too far down the page if of a sensitive disposition).
The direct connection between Melnikoff and the hate-filled site is clear from the terms and conditions of his own site, which establishes his rights over International Photo & Video News, Inc.
Melnikoff made his unorthodox views on Russia clear in a 2014 radio interview in which he asserts the degeneracy of Russians based on genetics and "selective breeding" over five generations.
Melnikoff clearly has an intense dislike for Putin and his cronies. But to argue that an entire nation is physiologically degenerate raises uncomfortable and obvious parallels with Europe's past tragedies. When Russian extremists such as Alexander Dugin make the reverse argument - that Ukrainians are degenerate, Russians superior - they are rightly put on the European Union's travel blacklist.
Yet Melnikoff in contrast is invited to open an exhibition on Brivibas iela - Freedom Street - right outside the Latvian cabinet office where the flags of Latvia and the European Union fly in tandem.
There are other questions worth asking.
Behind the Maidan exhibition is the "Soul of Ukraine Foundation." It is a corporation registered in Florida in 2014, the state in which Mr Melnikoff resides, and company documents show him to be one of the founders.
His daughter Anastassia, who prefers to write her surname as 'Melnikov' is the President of the Foundation. Sergey Alexeev is listed as the fund's co-ordinator in the Baltics and it is his 'Latvian Renaissance Foundation' that is listed as organizer of the Riga exhibition.
The Soul of Ukraine Foundation has charitable status and describes its purpose as "the support of Ukrainian people" listing the head of the Ukrainian Orthodox church as a patron. Its mission is "to create an expressive image of Ukraine in the word community."
That noble aim is to be achieved by means of Melnikoff's travelling photo exhibition.
Company documents show the revenue of the Foundation at March this year to be zero but with hopes that by the year's end it will rise to $2.75 million thanks to charitable donations and grants.
Projected expenses include $50,000 "subsistence allowance" for the directors of the Foundation, $115,000 for purchase of "four cars and a truck" and $30,000 for fuel.
But the Foundation has big plans which need a big budget. During 2015 it expects to show the Maidan exhibition in "58 major US cities" to an audience of 150 million at a cost of $650,000. If it is to meet that target, it will have to go some. So far the exhibition has not opened in a single US city, though the Foundation's website says it should do so in Jacksonville, Florida in November ("date and place to be confirmed").
It will also have to book airline tickets quickly to realize its plan of flying 100 Ukrainian dancers to the US to perform free of charge at a cost of $740,000.
The exhibition has so far appeared at four locations in Kyiv (including at the far right-wing Congress of Ukrainian Nationalists and the 'Blockbuster' entertainment center) plus the grand-sounding but little-known 'World Peace Forum' in Luxembourg, three weeks in Vina del Mar, Chile and now Riga.
Other revenue streams on the website offers countries to sign up to a different exhibition scheme called "Windows of the World" for a mere $150,000 with tiny Nepal apparently the only country to have taken the bait.
Yet another page offers a chance to "win the most expensive photo in the world" and there are plans to print a 1,000-run edition of the Maidan photos at $1,000 a copy along with other moneyspinners.
But more importantly from a Latvian perspective, the Foundation also lists the Latvian Ministry of Foreign Affairs as one of its supporters that has "shown commitment to support our fund and its mission." The ministry's logo is proudly displayed on the website and on every panel of the exhibition itself.
LSM asked the Ministry of Foreign Affairs if it was a supporter and was told:
"The Ministry of Foreign Affairs of Latvia did not take part in organization of the exhibition either in terms of financial or logistical support. Likewise, the Ministry does not possess information about promotional materials produced for the purpose of the exhibition."
That is in contrast to Melnikoff himself who told LSM the Foreign Ministry had not only invited him to bring the exhibition to Riga but had indeed provided logistical and organizational support (see audio file).
LSM asked if the ministry was happy to be associated with Melnikoff. The ministry replied:
"Being a state institution of a democratic country, which protects artistic expression, the Ministry categorically denounces any acts of vandalism against art exhibitions and expresses its support for freedom of speech. The Ministry of Foreign Affairs of Latvia also strongly disassociates itself from any radical, extremist and xenophobic views and underlines its support for freedom of expression in Latvia and beyond."
LSM also asked if the ministry had given permission for its logo to be used on the Foundation's website and was told:
"The logo here should not be associated with the author, but, as it stands in the webpage, with the exhibition currently shown in downtown Riga."
In short, the Foreign Ministry does not necessarily support Melnikoff's views but it does support the exhibition by Melnikoff and the Soul of Ukraine Foundation he founded.
Yet the Foreign Ministry had no hesitation in stopping Russian singers plying their trade in Latvia after they expressed extreme views not linked to their artistic activities.
The Cabinet Office told LSM that it had no role in the exhibition or its location right outside the building as that came within the remit of Riga City Council. According to Melnikoff himself, the Foreign Ministry obtained the necessary permits from Riga City Council.
But the Foreign Ministry is not the only Latvia connection. The other Latvian logo on the Foundation website belongs to the Latvia Renaissance Foundation, (LRF) of the aforementioned Alekseev which like the Soul of Ukraine Foundation is essentially a fund.
One of its aims seems to be to win compensation payments from Russia for the Soviet occupation of Latvia:
"We can find lots of excuses in order to not to pay. We can continue lying on shabby couches, drinking beer and chatting in forums that 'We aren't due to them anything!' The 'biomass' that is living in Russia now is living like that, but a real Human can't behave like that," the website says.
However the LRF also offers various financial services including "patriotic" tax reduction plans and says it will help investment and education in the country.
"These privileges are ABSOLUTELY legal (as opposed to offshore methods of tax evasion), patriotic and will be supported by Revenue Service (VID)," it promises.
Another important strand is the channeling of money from Russia to the Baltic states. Russians may be mere 'biomass' but it seems their money is as good as anyone else's.
The LRF is also keen to trumpet the Foreign Ministry's support and use its logo in promoting the Maidan exhibition, even going so far as to appeal for cash via its Facebook feed to print the Ministry's crest, saying permission to do so had been granted.
A press release put out by LRF explicitly states that the Maidan exhibition has the support of the Latvian Foreign Ministry and the Ukrainian embassy in Latvia.
The same press release says the exhibition will soon head for Canada, Australia, Japan and elsewhere.
Quite how organizing the Maidan exhibition contributes to "helping attract investments into the economy the Republic of Latvia" or giving grants to Latvian students is not specified.
Among the 'Friends' the LRF lists on its website is the Latvian Institute (LI), the body charged with promoting Latvia's image abroad. LSM asked what the nature of the relationship was and was told LI had simply granted permission for LRF to use its audio-visual materials.
Coincidentally, that is a privilege the LRF also has from Sergey Melnikoff. Just as soon as he has finished his Maidan project "the master" will begin work on a special book called "1,000 views of Latvia" and sponsors are being sought at €15,000 a pop, LRF promises.
There is no suggestion that Melnikoff, his associates or business entities are acting illegally. He may well have belatedly found his calling as official chronicler of the Maidan and decided to put his business talents to use in that direction.
The bravery of those manning the Maidan barricades is beyond question. Whether this exhibition and Latvia's support for Melnikoff is the best means of marking that bravery is at least worth asking, along with why a travelling exhibition about the People of Maidan isn't the work of the Ukrainian Ministry of Culture rather than a privately-owned corporation in Florida.
In order to let Mr Melnikoff give his own side of the issue, LSM interviewed him at the exhibition.
He finished by outlining his views on Russia and future plans for a gala event in Hollywood for the launch of his Maidan book.
