(Joe Scarnici/FilmMagic/Getty Images)

Invisible Children co-founder and director of the "Kony 2012? viral video Jason Russell, 33, is receiving medical care after witnesses reported he was seen naked, masturbating and disrupting traffic in San Diego's Pacific Beach neighborhood on Thursday, according to reports.

Russell allegedly was walking around an intersection wearing "speedo-like underwear." He then removed the underwear and made sexual gestures, sources told TMZ, which posted video of a publicly naked man purported to be Russell.

Several bystanders held Russell down until police arrived, ABC's San Diego affiliate reported.

Police said in a written statement that they had received several calls about disruptions by an unidentified male, apparently Russell, though they did not publicly identify him.

"Several callers reported the male was wearing only underwear and running into the street," said the statement released by San Diego police spokeswoman Lt. Andra Brown. "One caller reported that the male had removed his underwear and was nude, perhaps masturbating, but that was not confirmed by responding officers. The callers reported the underwear-clad male was in the street, interfering with traffic, screaming, yelling incoherently and pounding his fists on the sidewalk. Several people in the area tried to calm the male but he continued to act in a bizarre and irrational manner."

Brown told NBC San Diego in a video posted on the local station's website that the man was running into the roadway and interfering with traffic, although there were "no reports of actual collisions."

No charges were pending against the man, police said.

Ben Keesey, CEO of Invisible Children, said Russell had been dealing with health problems and was hospitalized after the incident on Thursday.

"Jason Russell was unfortunately hospitalized yesterday suffering from exhaustion, dehydration, and malnutrition. He is now receiving medical care and is focused on getting better," Keesey said in a statement. "The past two weeks have taken a severe emotional toll on all of us, Jason especially, and that toll manifested itself in an unfortunate incident yesterday."

In the past two weeks, a 30-minute video produced and voiced by Russell has gone viral. Supporters, many of whom learned about alleged Ugandan war lord Joseph Kony for the first time through the video, purchased t-shirts and action kits to help fund Invisible Children's quest to bring Kony to justice.

"Jason's passion and his work have done so much to help so many, and we are devastated to see him dealing with this personal health issue," Keesey said. "We will always love and support Jason, and we ask that you give his entire family privacy during this difficult time."

Russell, who has two children, is a filmmaker by trade. The viral video, which has logged over 100 million views, features the activist trying to teach his son, Gavin Danger, 5, about the warlord.

"We want to do some epic things because our time on Earth is so short," Russell told ABC News as his campaign was taking off. "Why not do this? Start here with Kony. Use him as the example of what injustice looks like in the world and then we're going to move to the next one and the next one."