VANCOUVER -- Police are asking witnesses to come forward weeks after a serious stabbing in East Vancouver that left a man "fighting for his life in hospital."

Authorities said the stabbing took place on Halloween night at Empire Field, where there were two violent altercations between two groups of people within the span of 90 minutes.

During the first altercation, which happened around 10:30 p.m. at Leeside Skatepark, a 31-year-old Vancouver resident was struck in the head by someone police described as a white man in his 20s who was wearing a Ghostbusters costume.

The second altercation happened around 11:45 p.m. near the public washrooms at the soccer field. Authorities said the same victim was stabbed "multiple times in the torso" by a different assailant, also described as a white man in his 20s.

"This was a violent assault that resulted in serious and life-threatening injuries," Sgt. Steve Addison said in a news release. "Detectives have not yet been able to identify the people responsible, and are asking for the public's help to solve the crime."

The victim collapsed a short distance from the park, and spent several days in hospital recovering from the attack.

Police said there were dozens of people at Empire Field at the time, and urged anyone with information on the people responsible to come forward. The stabbing suspect is believed to have been wearing dark clothes and carrying a shoulder bag with distinctive red and white stripes.

"We know some witnesses used their phones to record the altercations and we’re asking for anyone with pictures or video to do the right thing and call investigators," Addison said.