PORTSMOUTH -- The suspect was taken into custody without incident by the FBI in Virginia Beach around 5:10 p.m., spokeswoman Misty Holley told KVUE's sister station WVEC.
No further details about his capture have been released.
It appears the lockdown has been lifted at Naval Medical Center Portsmouth.
The victim was identified as Petty Officer 2nd Class Justin Powell. His surgery was sucessful, Capt. Johansson said during a media briefing around 5:45 p.m. Powell remains in critical condition.
According to biographical information provided by the Navy, Harwell was assigned to the frigate Elrod until November, then to the hospital. He has been assigned to the TPU since Feb. 5.
Capt. Michael "Jake" Johansson characterized the search for the suspect as slow and methodical. He said by Friday afternoon they had covered quite a few floors at the hospital.
"We're doing a systematic, room by room, building by building search," said Johansson.
The victim sustained multiple stab wounds to his chest and neck. He was in surgery with critical injuries and has not been identified.
Johansson said the victim's wife is at the hospital with her husband and is in as "good of spirits as possible in this situation."
Joe Gomez stood outside the gates watching the situation unfold.
"It's been crazy. It's like five different swat teams out here. A lot of helicopters and police presence," Gomez said.
But he was more concerned about his family barricaded in the Navy hospital.
"They shut the base down. They took them into a conference room and put them in a closet or something, then the room didn't have a lock on the door so they had push tables and stuff in front of the door," Gomez said.
The Naval Medical Center posted on their facebook page around 3 p.m. that they hoped to begin evacuating soon. "Patients first followed by staff. The evacuation will be done in an orderly manner as directed," it read.
Capt. Johansson said they are working with the hospital to determine essential personnel before shift change Friday afternoon.
Two schools were on lockdown as a precaution. Parkview Elementary School and Norcom High School were on partial lockdowns but were both dismissed on time. Police are stationed outside the school, said Det. Misty Holley.
Alison Todd said she was just getting into her car when she say police converge on the campus.
"As I got into my car, about five police cars came around. Before I could pull off, about 10 more came around and then before I could turn around, about 20 more came and I just knew something serious had happened," she said.
He did not have any information about a motive for the stabbing.
For anyone who has an appointment or business at the installation, you should stay away until further notice.
Just Thursday, the installation underwent an "active shooter" drill. Capt. Johansson said the drill was very fortuitous.
"Pretty much everybody that was at that exercise yesterday showed up to day," Johansson said.
Portsmouth Police are assisting the Navy with the situation. Patrol officers, plain clothes detectives, SWAT and some command staff are taking part in the search, said Det. Holley.
Norfolk Police with an armored vehicle, the Chesapeake Police SWAT, NCIS and Homeland Security officers are also assisting.
NSA Hampton Roads provides consistent, operationally ready and secure shore installation support services at Naval Support Activity Hampton Roads (NSA HR) Headquarters (to include Supply Depot Annex and Camp Allen Marine Corps), Lafayette River Annex, NSA HR-Portsmouth, and NSA HR Northwest Annex, allowing tenant activities to dedicate their resources to warfighting, forward operations and combat readiness.