Suspect Mark Geisenheyner in Pennsylvania country home shootings shot dead

A man suspected of shooting dead a two-year-old boy and his stepfather in a holiday massacre killed himself during a tense stand-off with police, law enforcement sources say.

Two 30-strong SWAT teams surrounded a home in Marcus Hook, Pennsylvania, for hours this moing, firing percussion bombs and tear gas into the house in an attempt to drive the man out.

Shortly before midday a bystander reported a body being brought out of the house, and a police source said the man 'did himself in'.

Police had launched a massive manhunt for the gunman after five people, including a professor from New York, were shot in the head in what was described as an 'execution-style' killing in Douglass Township, Pennsylvania.

Massacre: Little Gregory Erdmann, two, was killed in the shooting and Monica Shay, a professor from New York, was not expected to survive after being critically injured. All five victims were shot in the head

A source in the Delaware County prosecutor's office told the Philadelphia Enquirer that the man, described as 'a person of interest' in the horrific shootings, 'did himself in'.

The man has not yet been named. The owner of the house allegedly called a local radio station and said a friend had arrived at his home late on Sunday night saying he needed a place to hide, after a 'robbery had gone bad'.

The shooting happened on Saturday night, at a home in Douglass Township owned by Monica Shay, an arts professor from New York, and her husband Paul.

The couple were hosting their nephew, Joseph Shay, his girlfriend and her two-year-old son at their home in Douglass Township for the July 4th weekend.

Critical condition: Kathryn Erdmann, 37, was badly wounded in the shooting. She managed to crawl to the phone and call police

The little boy, Gregory Erdmann, died at the scene along with Joseph, 43. His mother, Kathryn, who lives with Gregory in Fall River, Massachusetts, is in a critical condition in hospital.

A relative said Mrs Shay had 'no hope of survival' after she too was shot in the head, and her husband was also described as being in a critical condition.

It has emerged that Joseph had spent time in jail for drug dealing and grand larceny, but he was staying with his aunt and uncle and they were helping him tu his life around.

Miss Erdmann, 37, crawled to the phone and dialled 911 after the shootings, which happened at about 10.30pm on Saturday.

Mr and Mrs Shay live in New York City but keep Mrs Shay's childhood home as a weekend retreat, and had spent years renovating the property.

Mr Shay, 64, owns a plumbing business and Mrs Shay, 58, is an associate professor at the Pratt Institute, where she is director of the arts and cultural management program.

Her brother, Edward Newbold, said he had been told there was 'no hope - zero, zero, zero' that his sister would survive.

He told ABC6: 'She was beautiful, loved. She was a wonderful beautiful person. I miss her so much.'

Friends told the Philadelphia Inquirer Mr Shay gave his nephew a job when he was released from prison for grand larceny last year, and had been helping his rehabilitation.

He spent two years in a New York jail for the theft, and before that spent eight years in Atlantic County, New Jersey, for a drug dealing conviction.

Search: SWAT teams arrive in Douglass Township to scour the surrounding woods for the gunman after the shooting on Saturday night

Dan Hoyt, a neighbour of the Shays in Manhattan, told the New York Post: 'It's bizarre, a shock - and a whole family.

'He (Joseph Shay) was just coming out of jail, and Paul took him in. He gave him a place to work at his company, a Real Good Plumber.

'Paul was the kind of guy who hired people most wouldn't. He liked to help people out and get them on their feet.

'His nephew was in and out of trouble with police, and Paul was helping him out.'

The surviving victims, who have not yet been able to speak to investigators, were all airlifted to hospital for treatment.

Hunt: A helicopter joins the search for the gunman above woodland in rural Pennsylvania

Desperate hunt: A police officer and a sniffer dog search for the gunman in rural Pennsylvania yesterday moing after Saturday's shooting

Mr Shay was found outside, but the others were discovered in different rooms inside the house.

Montgomery County First Assistant District Attoey Kevin R. Steele told the Inquirer: 'They were all shot in the head, which is unusual, but beyond that we don't have anything else to suggest this was a targeted hit.'

SWAT teams and police dogs scoured the rural area for hours afterwards, but could find no trace of the gunman.

The couple bought the house from Mrs Shay's mother in 2003. It had been destroyed in a fire and they spent their weekends restoring it.

Edward Newbold, 60, Mrs Shay's brother, said the house was still not finished. He told ABC 6: 'It was going to be a lifetime project to finish that house.'