Authorities are trying to piece together a crime in the Long Beach area with very few leads, excluding the existence of a powerful video that emerged a few days after the incident, which occurred early last week.

Officials with the Los Angeles Sheriff’s Department (LASD) Transit Policing Division believe the beating of a man by a female suspect on a Metro Blue Line train in Long Beach happened the evening of Monday, August 1, according to a witness who posted a video of the incident on Facebook.

The graphic footage shows the young female suspect kicking the older victim directly in the face, causing him to lose balance and fall on his knees in between two seats. She eventually uses a handrail as support to jump on the man’s back and stomp on him until he is laying on the floor. The witness, who recorded the video is heard saying “don’t kill him now,” as the man falls onto the ground.

In a Facebook post, the witness said the woman, who appeared to be in her 20s, beat the man after he allegedly called her the N-word.

Authorities did not know about the incident until the video was posted on social media, and they have since then spoken with the witness who posted the footage, according to LASD spokesman Ramon Montenegro.

“Using the timeline [the witness] gave us, we have been able to narrow it down to a group of trains that were in service at that time to request video,” Montenegro said.

Although no one has come forward with information yet, Montenegro was hopeful, based on the progress made.

“We’re just a little bit closer,” he said.

The incident is the second known recorded attack on a Metro Blue Line in recent months that has led to an investigation.

An 18-year-old Long Beach woman was sentenced in January to 270 days in jail for an attempted robbery attack on a Metro Blue Line train in the Rancho Dominguez area.