Police are questioning someone after a man was pushed in front of a subway train and killed.

So far, no formal charges have been filed.

Investigators have released surveillance video of the incident taken at the 49th Street N/Q/R station in Midtown.

The tape shows two men arguing just before one pushed the other around 12:30 p.m. Monday.

Police say Ki-Suck Han, 58, tried to get back onto the platform but was hit by a southbound Q train.

Witnesses say the attacker was mumbling to himself before he pushed the victim.

Investigators say the man they are looking for is between 20 and 30 years old, around 5-feet-9-inches to 5-feet-10-inches tall and weighing between 180 and 190 pounds.

Anyone with information on the case should contact the Crime Stoppers hotline at 1-800-577-TIPS, or text CRIMES and then enter TIP577, or visit www.nypdcrimestoppers.com.