A spokesperson for Twitch said the company removed a livestream by the less than two minutes after the violence started.
The suspected shooter, an 18-year-old white man, shot and killed 10 people and injured three others at a supermarket in a predominantly Black area, authorities said. Officials said 11 of the 13 people shot are Black.
Social media companies have struggled to keep up with a torrent of violent content on their platforms. So Twitch's performance may be applauded by some while still criticized by others.
The company did not immediately respond to follow-up questions about whether the suspect was still actively firing when the livestream was halted.
A portion of the Twitch livestream obtained by CNN shows the shooter pulling up to a Tops Friendly Markets store in Buffalo, New York, before opening fire on people Saturday afternoon.
The video is taken from the point of view of the shooter as he's driving into the parking lot of the Tops market.
The shooter, who is seen in the rearview mirror wearing a helmet, is heard saying, "Just got to go for it" before he pulls into the front of the store.
In the video, store patrons can be seen walking through the parking lot as the suspect drives up.
In a news conference on Saturday evening, Buffalo Police Commissioner Joseph Gramaglia said the shooting was livestreamed.
In a statement sent to CNN, Twitch confirmed the shooting was streamed and said the user "has been indefinitely suspended from our service, and we are taking all appropriate action, including monitoring for any accounts rebroadcasting this content."
CNN is not airing the video at this time.
