(CNN) -- Police in Pennsylvania mounted an intense search Monday in the Philadelphia suburbs for a man suspected of killing his ex-wife and five former in-laws, the district attorney for Montgomery County, Pennsylvania, said at a Monday night press conference.

Bradley William Stone of Pennsburg killed his ex-wife and her mother, grandmother and sister, as well as the sister's husband and 14-year-old daughter, said District Attorney Risa Vetri Ferman.

But Stone didn't harm his two daughters, who were living with his ex-wife. He took them to a neighbor's residence in Pennsburg, the last place he was seen, Ferman said.

"We do not know where he is," Ferman said. "We do not have vehicle information. We actually recovered his vehicle and his personal cellphone so we do not have information how he might be traveling."

She didn't provide a motive for the slayings. Stone was described as armed and dangerous.

Late Monday night, police agencies descended on Doylestown, Pennsylvania, to investigate a possible sighting of Stone, according to a source with knowledge of the investigation. Doylestown is about 25 miles from Pennsburg.

A "shelter in place" had been ordered in the surrounding area where the sighting occurred, according to the source, and K-9 units have been asked to respond to the area as well.

Suspect led American Legion post

The killings broke the calm in several small towns in Montgomery County, the second wealthiest county in Pennsylvania and the 51st wealthiest in the United States, according to the county government web page.

Stone served as a reservist in the U.S. Marines until 2011, mainly as a meteorologist, according to the Marines. He spent a few months in Iraq in 2008.

William Schafte of Harleysville, who described himself as a friend, said Stone was a "good guy" who helped people who needed money or a hand, according to the Morning Call newspaper of Allentown, Pennsylvania.

Stone served as president of the American Legion William E. Hare Post 206 in Lansdale about a decade ago, said the current post commander John Gillmer, the Morning Call reported.

"He was always on the honor guard and stuff like that for parades," Gillmer told the Morning Call. "I was shocked, I couldn't believe it. ... I never would have thought it was one of our guys."

911 hangup call started investigation

Ferman said the investigation started at 4:25 a.m. with a 911 hangup call directing police to the town of Lansdale, 28 miles northwest of Philadelphia.

When police arrived, they found two slain women: Stone's former mother-in-law and former grandmother-in-law, Ferman said.

At 4:55 a.m. a neighbor of Stone's ex-wife called 911, Ferman said. Police went to an apartment in Lower Salford and found Nicole Stone, 33, dead.

Another neighbor, Michele Brewster said she heard a loud crash and shattering glass.

"Thought I heard a gunshot, but wasn't sure," she said. "A few minutes later I saw flashlights -- it was the cops putting up police tape so I went outside."

Brewster said she asked an officer if gunshots had been fired. He said yes.

"I asked him if she was dead," Brewster said, "but he said he couldn't tell me that."

At 5:30 a.m. Stone delivered his two daughters to a neighbor in Pennsburg, Ferman said.

"That was the last time he was seen by anyone," she said. "I think it's of great significance the children are safe right now."

About 8 a.m., police went to the home of Nicole Stone's sister, Patricia Flick, in Souderton. Officers found Flick, her husband and the couple's 14-year-old daughter dead, Ferman said.

The sister's 17-year-old son was wounded and was being treated at a Philadelphia hospital, Ferman said.

Suspect may be wearing fatigues

Though last discovered, it appears the killings in Souderton took place first, the district attorney said.

Ferman's office said Stone may be wearing military fatigues, in either sand or green color.

According to Montgomery County court documents found online, the Stones divorced in 2009.

In family court papers, Stone's ex-wife said he claimed in a 2011 hearing that he was "permanently disabled," according to the Veterans Administration, but that he had not applied for Social Security disability benefits.

The Marine Corps told CNN it has no record of Stone being injured.

"Earlier today we indicated that he does on occasion use a cane or a walker, but he may or may not be using those devices," Ferman said at the press conference. "It's been indicated to us it may not have been necessary. ... If he has escaped he might be seen using a device or not."

CNN affiliate WPVI said police originally thought Stone was holed up inside the house in Lansdale, so officers surrounded the residence.

Heavily armed SWAT teams tossed flash-bang devices into the house and stormed the residence, but police said Stone was not inside.

Fast Facts: Rampage killings in the United States

CNN's Kristina Sgueglia and Lawrence Crook contributed to this article.