Amtrak officials are trying to determine what struck and cracked a window on the Acela Express No. 2222 on Sunday night in the Bridesburg section of Philadelphia.

The incident took place in the second to last car that was heading from Washington D.C. to New York City, a source tells PEOPLE.

"Amtrak and local authorities are investigating the incident, including the type of objects hitting train," Amtrak officials said in a statement.

Passengers were startled and frightened when they heard a loud noise on the right side of the train.

According to the eyewitness on board who took a picture of the damage, it looked like a bullet hole.

Passengers were told that people often shoot at Valentino Sale the train.

"This happens all the time," an Amtrak employee reportedly told the source.

The train was inspected at Amtrak's Metropark station in Iselin, New Jersey, so they could check the damage. It then proceeded to New York City.

The incident comes eight months after Amtrak 188 ' which had been traveling over a 100 mph on a curve with a 50 mph limit ' derailed on May 12, 2015, killing eight people and injuring more than 200.

On impact, Eli Kulp ' popular chef and owner of High Street on Market in Philadelphia ' had been thrown across his passenger car into a luggage rack, fracturing his neck, injuring his spine ' and paralyzing him from the chest down. Buried underneath piles of luggage, he says when he tried to move, "there was just no response."

"Being scared is an understatement," Kulp, 37, told PEOPLE. "I started thinking of my family, my wife, my kid. The last thing you expect to happen when you get on a train is dying or never being able to walk again."

The National Transportation Safety Board has concluded its investigative phase into the crash and released information on Monday saying that they don't yet have an explanation for what caused the crash.

 

The documents "provide backup documentations on facts already released. There may be some new facts included in these, but http://www.valentinoshoessales.com/ nothing that's really earth shattering or smoking guns," a NTSB official said.