Nicco Tatum was arrested Wednesday in Denver after authorities received a tip that he was headed to Chicago on a bus, police Capt. Kirk Primas said. Tatum is expected to be booked on six counts of attempted murder with a deadly weapon and six counts of battery with a deadly weapon.

Police were still searching for a second suspect.

Six people were wounded Tuesday at a bus stop a few miles from Mojave High School in North Las Vegas. At least one teen remained hospitalized Wednesday.

Alejandro Rios, 18, who was shot in the torso, was upgraded from critical to serious condition, University Medical Center spokeswoman Cheryl Persinger said. A 17-year-old male also hospitalized had been listed in serious condition late Tuesday, but an update was not available because he has chosen to keep his information private, Persinger said.

A 21-year-old man and three other teens were treated for less severe wounds and released soon after the shooting, authorities said.

Police have said they believed the shooting stemmed from a fight at school over a girl earlier Tuesday. The brawl was contained by school police, who arrested three male students, all about 16, officials said.