Six teenagers were released on bail after being arrested in connection with the brutal beating of an off-duty gay police officer trainee in Liverpool, England, on Sunday.

Initial reports said that James Parkes, 22, was bashed by a gang of 13, but the BBC reported Tuesday that he may have been attacked by as many as 20 people. Four boys, ages 14, 17, and two who are 15, remained in police custody on suspicion of assault.

Detectives have acquired closed-circuit television footage for the investigation. It is being treated as classified. Detective Tim Keelan is asking for witnesses of the assault on Sunday evening in Liverpool's gay neighborhood to step forward.

"We are treating the assault as a homophobic hate crime, and this incident shows there are still some people who have not learned that crimes of this type are completely unacceptable," he told the BBC.

Parkes was with his boyfriend and two friends at the time of the assault; one of his companions was also punched in the face. Parkes is hospitalized in critical condition with multiple skull fractures, a fractured eye socket, and a fractured cheekbone.