President Joe Biden called Russian President Vladimir Putin a “war criminal” on Monday after sickening images of dead civilian bodies filling mass graves and littering the streets of the Ukrainian city Bucha surfaced over the weekend. “We have to gather the information [to prove Putin is committing war crimes], we have to continue to provide Ukraine with the weapons they need to continue to fight and we have to get all the details so this can be an actual – have a war crime trial,” Biden told the press. Ukrainian President Volodymyr Zelensky visited the ruins of Bucha on Monday. He urged the m…