A view of the roughly 20-inch-wide pipe where escaped prisoner David M. Watson hid in Jessup, Md., before he was caught. (Courtesy of Howard County Police department)

A fugitive who had been on the run for six days was found lying in a 20-inch-wide drainage pipe just half a mile from the Maryland psychiatric hospital to which he was being taken, authorities said.

David M. Watson, 28, was ­captured late Wednesday not far from Clifton T. Perkins Hospital Center, the state’s maximum-security psychiatric hospital in Jessup, from where he had escaped after pushing a guard as he was being brought there in a van.

Watson is serving a 100-year sentence in a correctional facility in Delaware for attempted murder in that state. Authorities had launched efforts to find him since his escape but had suspended their ground search four days ago, thinking he was no longer in the area.

But Wednesday morning, they got a call. It was what Howard County Police Chief Gary Gardner called the “first, major breakthrough.”

David Watson was captured after eluding police for six days. (Courtesy of Howard County Police )

At a Thursday news conference, authorities detailed how they found Watson.

The person, who called 911 about 9:30 a.m. Wednesday, reported seeing a man, dressed in dark pants, a hard hat and a safety vest, near the railroad tracks behind a building along Dorsey Run Road, an industrial area. Once the man was spotted, he ran into a heavily wooded area nearby, the caller told police.

A law enforcement team was dispatched, and they talked to several workers in the area who were “ruled out as suspects,” authorities said.

But while investigating, they learned of a theft from a storage building about a mile away. A safety vest and hard hat were gone, they said.

When searching the area where the caller reported seeing the man, authorities found more clues: packing materials inside a concrete drainage tunnel and footprints.

They relaunched a full ground search, with K-9 units and bloodhounds, police officers from Howard and Anne Arundel counties, units from Maryland State Police and CSX Police, and helicopters. They checked drainage pipes in the area and found nothing.

Then, about 9:40 p.m., officers with night vision equipment rechecked one of the pipes, and found their man.

Watson was hiding — lying “face front,” Gardner said, inside a roughly 20-inch-wide drainage pipe — one of many they had searched previously, officials said. He was just a few hundred yards from where the caller had reported seeing him, authorities said.

Watson briefly struggled with law enforcement before being taken into custody, according to Gardner. He said Watson was in “overall good health” and had suffered minor scrapes during his time in the woods.

After talking with him, authorities said, and from footprints and bloodhound trails, they realized Watson had been moving north, east and west within a roughly one- to two-mile radius of the Perkins facility since his escape. He hid or rested in drainage pipes.

After capturing Watson and searching the area, officials said they found one drainage pipe where he had apparently bedded down using wood fiber and packing materials.

The person who made the call to authorities to report seeing Watson will receive a cash reward, Gardner said.

How exactly Watson escaped is still under investigation.

Guards were transporting Watson on Friday to the Perkins facility from the Wicomico County Detention Center in Maryland. He allegedly pushed a guard to the ground and ran into the woods near Dorsey Run Road. It was not clear, officials said, how Watson had gotten out of handcuffs and a waist chain, which were found near the van.

The initial investigation found that Watson didn’t have assistance in escaping from outside the Perkins facility, Gardner said Thursday. He said officials weren’t sure whether it was an “impulsive escape,” and it didn’t appear to be a “long-term plan.” He said Watson’s escape appeared to have “evolved during transport.”

Authorities had called off the ground search for Watson on Saturday, saying at the time that they had found nothing to show he was still in the area.

Investigators had gone to businesses and homes in the Jessup area to ask people to be on the lookout and to check surveillance videos from cameras.

Until Wednesday, they had not heard much in terms of sightings, officials said.

“This was the first sighting and tip that led to an extensive search,” Gardner said.

Watson was convicted in 2013 of attempted murder after firing a rifle into the house of a Delaware police officer, according to the Delaware News Journal. Online court records in Maryland show he was found incompetent to stand trial in 2014.

Watson was to be transported Thursday to Delaware. He also faces charges in Wicomico County, Md., for attempted murder of law enforcement officers, and in Howard County for assault and escape, police said.