Two Muslim teens were attacked outside a mosque in Brooklyn this weekend in what advocates are calling a bias incident.

Police confirmed that the attack took place around 1:15 a.m. Sunday in front of Muslim Community Center of Brooklyn at 53rd Street near Third Avenue in Sunset Park. One of the victims, 16-year-old Ahmad Emrech, was taking a break from late night prayers when he was beaten by the assailant, according to the Council on American-Islamic Relations (CAIR), who released a statement about the attack on Facebook.

Another youth, also 16, was also reportedly chased and attacked when he rode his bike past the assailant as Emrech was being beaten. The assailant was reportedly heard shouting slurs at his victims, including, "You f**king terrorist," and, "You Muslims are the cause of all the problems of the world."

Emrech was punched, thrown to the ground, kicked in the face and stomped on. He sustained a concussion, cuts, bruises, and severe swelling to his eye, head and face. He was taken to Lutheran Hospital for treatment. The second victim also suffered from a swollen black eye.

You can see surveillance video and followup photos of the attack in the CBS report below.

Mohamed Bahe, the director of the mosque, told Buzzfeed that the teens were investigating "a tinted and suspicious vehicle" before the attack.

"We had two volunteers, and they saw a suspicious car parked outside of our entrance. They looked at the car, trying to figure out who’s inside. They saw a woman and they asked if she needed help. Then all of a sudden a guy comes across running from the street and punches him and knocks him down. He was stomping him and kicking him," said Bahe.

One teen suffered a concussion, cuts, bruises and a badly swollen eye, and was taken to a local hospital. The other teen suffered a black eye.

While police did not offer any other information about the incident to Gothamist except to say it wasn't being investigated as a hate crime, a law enforcement source explained to Reuters why investigators had ruled this out as a bias crime: "He said the two youths were harassing a 40-year-old woman in a car and her 37-year-old boyfriend assaulted them."

Another police source told Buzzfeed a few more details: "These two individuals were standing outside of the vehicle with a woman who I understand was dressed quite provocatively. They were not in any Muslim attire....The hate crimes unit did interview both victims, who said the suspect didn’t say anything anti-Muslim to them."

If that sounds suitably vague, a spokesperson was a little more blunt with DNAInfo: "They were hitting on [the suspect's girlfriend]."

Bahe called this "a blatant cover-up," and non-profit group Muslims Giving Back decried the decision not to categorize it as a bias crime: "One of the victims heard the attacker shout "Terrorist!" while being punched to the ground. This is absolutely a HATE crime."

CAIR also noted that the Muslim Community Center had repeatedly asked the local precinct to increase patrols in the area during the hours of late night prayers during Ramadan. "The slurs heard during the assault indicate that the attack may have been fueled by hatred of the victims’ faith, thereby warranting an investigation by law enforcement into a possible bias motive," said CAIR-NY Executive Director Afaf Nasher.

Public Advocate Letitia James also urged the NYPD to investigate the incident as a hate crime in a statement:

“I am deeply disgusted by the assault of two Muslim teenagers that occurred outside of their mosque early this holiday weekend. This type of hate and violence will never be tolerated in New York City, especially during the holy month of Ramadan. I urge the NYPD to investigate this as a hate crime, and continue to call on all New Yorkers to report hate crimes against any and all communities. New York City should be a safe haven for people from all walks of life and we must do all we can to prevent these vicious and hateful attacks.”

“Any person who has information about this crime is encouraged to contact NYPD Crime Stoppers at 1-800-577-TIPS.”