A man was killed Monday evening when he jumped from a Metro station mezzanine onto the rail tracks, causing major delays on the Red Line during the peak of the evening commute and trapping riders on a train in 90-plus degree heat without air conditioning.

The death occurred about 6:10 p.m. at the Grosvenor station, Metro spokeswoman Lisa Farbstein said. Preliminary reports indicate the man jumped from the upper platform onto the tracks, she said. The unidentified man was not hit by a train, she said, but died at the scene.