One man is in jail in connection with a Christmas morning stabbing at a MAX platform.

Saul Vela, 19, was arrested Tuesday morning and is charged with first degree robbery and first degree assault, according to a Portland Police Bureau release.

At 6:40 a.m., Portland police found an injured man at the Southwest First Avenue and Southwest Oak Street MAX platform, according to spokesman Sgt. Chris Burley. The platform was closed for hours during an investigation.

Witnesses and the man said that three people were approached at the platform by a person who had a gun. That person demanded they empty their pockets.

Two more people came to back up the robber, said police.

The man waiting for a train was stabbed and assaulted while the other two people ran away. Police at first said that two people had been detained on suspicion of being involved. Vela has been the only arrest so far.

Portland police say the man sustained a serious, but not life-threatening injury. He is still in the hospital, where he was taken by ambulance after the stabbing.

After the assault, the three suspects also ran.

Burley refused to identify the other two suspects unless they are also arrested.

Police have asked anyone with information about the incident to call Portland Police Bureau Detective Division Robbery Detail Det. Heidi Housley at 503-823-1063 or email Heidi.Housley.portlandoregon.gov .