MEMPHIS -- Three people were shot Monday night at a vigil to honor a teen killed by a stray bullet, reports CBS affiliate WREG.

The shooting happened around 8 p.m. at the vigil for Myneisha Johnson, an 18-year-old killed by a stray bullet in 2016 in downtown Memphis. Johnson was the mother of a one-year-old child and was scheduled to graduate high school before she was shot and killed. Friends had gathered to mark the one-year anniversary of her death.

Witnesses say as soon as they started lighting candles, two cars pulled up and the occupants started shooting at each other. One witness told WREG she heard 20 gunshots.

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Police said one of the victims is in critical condition and two others are noncritical. Police originally said there was a fourth victim but later said they could only confirm three who were shot; they are checking local hospitals for any other victims, the station reports.

Police think the shots were fired from vehicles but have not confirmed that yet, according to WREG. So far, there have been no arrests.