Investigators arrested Erbie Bowser, 44, on Wednesday night at the second crime scene, DeSoto police Cpl. Melissa Franks said. Charges are pending, she said.
Four people were also wounded in the attacks. Franks said the attacks were a domestic incident and that investigators were trying to determine how Bowser knew the victims.
The first shooting took place at a house in southwest Dallas late Wednesday and the second happened about 15 minutes later in DeSoto, some 10 miles away, Dallas police Sgt. Warren Mitchell said.
Police were called around 10:30 p.m. to the home in Dallas where they found four gunshot victims. A mother and her daughter were killed and a 14-year-old boy and a 17-year-old girl were wounded. A relative discovered the bodies.
The gunman then fled to DeSoto, where he is suspected of killing two women. Two boys, ages 11 and 13, were shot but survived that attack, Franks said.
A neighbor in DeSoto, Tommy Johnson, said he heard a loud boom Wednesday night coming from the direction of the home where the victims were later found.
"We thought it was coming from upstairs, because the kids are always upstairs making noise," Johnson said. "I went up and asked, 'Did y'all hear anything?' and one of my daughters said it came from outside. So I peeped out the front and that's when I saw a bunch of officers walking down the sidewalk and about 10 houses up."
Franks said she could not confirm that a grenade or other explosive device had been used in the DeSoto attack pending the results of an ATF and Dallas bomb squad investigation.
Neighbors wearing nightclothes came out of their homes before dawn Thursday to watch as police investigated the DeSoto crime scene.
The Dallas Mavericks said Thursday that Bowser was a dancer for the team, performing with the Dallas Mavs ManiAACs. The team describes the dance troupe as "beefy men" who entertain fans during games. Bowser danced with the group from 2002 to 2009.
He worked for nearly a decade as a special education teacher in the Dallas suburb of Mesquite. School district spokeswoman Laura Jobe said Thursday he resigned in 2010 "on good terms." He also worked for a couple of seasons as a football coach at West Mesquite High School, she said.
Copyright 2013 The Associated Press.