Police cruisers surround Club 13 on Main Street after a gunman sprayed bullets at a wedding reception on Saturday. (Kevin Engstrom/SunMedia)

Winnipeg police are searching for a man who shot three people at a wedding reception on Saturday night, killing a woman and wounding two other people.

Police were called to the Polish Combatants Association Club on Main Street at about 11:15 p.m. They were told a man had fired at guests after slipping through the back door, which had been kept open to let in fresh air.

A woman identified as Cheryl Robert, 50, of Winnipeg was shot in the head and later died in hospital, police said.

Her common-law husband, also 50, and a woman, 31, were treated in hospital for their wounds and released, said Staff Sgt. Andrew Smith.

Police interview witnesses who were detained on a city transit bus following Saturday's shooting. (Kevin Engstrom/SunMedia)

About 100 guests were at the reception for a couple identified as Jason and Angel.

Relatives said the wedding was a celebration of the couple's already 18-year relationship.

Sheila Sinclair, the bride's sister-in-law, said at first she thought the noise was the sound of balloons popping, then her husband told her to duck. Sinclair saw Robert hit the ground and went over to check for a pulse.

"I just held on to her and yelled out, 'Does anybody know CPR?'" she said.

Police don't know if the suspect was at the wedding earlier, or if he was working alone, said Const. Jacqueline Chaput.

"His actions were clearly a cowardly and violent assault against innocent people here," she said.

There were known gang members at the reception, but there is no evidence the violence was gang related, she said.

No arrests have been made.