[UPDATE BELOW] An NYPD Traffic Enforcement Agent was fatally struck in Midtown Manhattan this afternoon, according to authorities.

The traffic agent was struck by a driver at around 2:30 p.m., at 44th Street between Madison and Fifth Ave.

Sources say the agent may have been standing in front of a truck, and was struck when the driver did not see him and moved forward. CBS News reports the agent was transported to a nearby hospital, where he died upon arrival. Police Commissioner Ray Kelly has been called to the scene to investigate; we will update with more details as they become available.

Update 4:29 p.m.: A witness tells us:

I saw what looked like a Cornell University bus rear ended a truck but there was a man with blood coming out of his head lying on the road near the wheel of the truck. I looked by about 15 minutes and I think I saw a white tarp over the man, at this point the block was blocked off.

Update 7:00 p.m.: A spokesman for Cornell University tells us one of their Campus to Campus buses was struck by the vehicle that had previously struck and killed the NYPD traffic agent.

"Our bus remained on the scene, and our driver is cooperating with Police on the scene. The driver is not expected to be charged in connection with the accident, and Cornell University will continue to cooperate fully with local police as they investigate this tragic accident," the spokesperson said.