ELKHART, Ind. -- Police in Indiana and Illinois are still looking for a man who's believed to have abducted his ex-girlfriend and their four children.

• Amber Alert: Abducted Family

Police said two cars connected to the incident have been recovered, but there's no clue as to the whereabouts of the captives.

An arrest warrant has been issued for 30-year-old Jerry D. White.

Police said White broke into his ex-girlfriend's house and shot her sister's boyfriend. They said he then held his ex-girlfriend and her four children hostage for about nine hours Saturday morning before forcing them into a car and fleeing, possibly to Chicago, police said.

Elkhart police who issued an Amber Alert for the woman and her children said the White was armed and dangerous and his hostages were in extreme danger. Police said White has a long criminal history that includes domestic battery.

Police said the oldest of the children has severe asthma and needs to use a ventilator but that device was left behind in the home in Elkhart.

Detective Sgt. Bill Wargo of the Elkhart Police Department said an arrest warrant for attempted murder and several counts of confinement had been issued for White.

Police did not release the name of the man injured in the shooting but Wargo said he was in critical condition and his prognosis was poor.

White, who has a long criminal history that includes domestic battery, may have fled to Chicago -- about 90 miles to the west -- with his ex-girlfriend, Kimberly N. Walker, 31, and their four children, Wargo said.

Wargo said White and Walker once lived in Chicago and White has family there.

Wargo said White is the father of Walker's four children. Police said the children are:

Jaylan Walker, a 9-year-old black male who is 4 feet tall and weighs 60 pounds. He was last seen wearing green pants and striped green shirt with a beige coat.

Justin Walker, an 8-year-old black male who is 4 feet tall and weighs 60 pounds. He was last seen wearing a navy blue fleece warm-up outfit and a blue coat.

Kyara Walker, a 6-year-old black female who is 3 feet tall and weighs 35 pounds. She was last seen wearing beige pants, a pink coat and blue shoes.

Kayla Walker, a 16-month-old black female who was last seen wearing beige pants, a burgundy coat and a cream colored hat.

Police said White had apparently been harassing Kimberly Walker over the last few days, and her sister and her sister's boyfriend had decided to stay with her and the children.

On Friday, Walker called police and said White had confined her in her car with a weapon before stealing the vehicle.

About 2 a.m., White broke into Walker's house and entered a bedroom, shooting the boyfriend of Walker's sister, leaving him critically wounded with two gunshot wounds, Wargo said.

Police said White then held Walker, the four children, Walker's sister and her boyfriend hostage until about 11:30 a.m., when he forced his five hostages into Walker's beige 1993 two-door Saturn and fled.

After they left, Walker's sister called police and reported the shooting and abductions.

Police said Kimberly Walker is black and 5 feet 6 inches tall and weighs 105 pounds. She was last seen wearing jeans, a navy and light blue jacket and tennis shoes, police said.

White is a black man who is 5 feet 10 inches tall, weighs 165 pounds, and has black hair and brown eyes, police said.

Police said anyone who knows the whereabouts of White, Kimberly Walker or the children should call 888-582-6237.