A Florida man suspected of gunning down four family members at a Thanksgiving dinner was arrested Saturday night in the Florida Keys after a weekslong manhunt, authorities said.

Jupiter Police Sgt. Scott Pascarella said Paul Merhige, 35, was taken into custody without a struggle by U.S. Marshals and Monroe County Sheriff's deputies at a motel on Long Key. Pascarella credited the TV show "America's Most Wanted" for the tip that led to Merhige's capture.

SLIDESHOW: Thanksgiving Killings

Merhige has been the subject of a massive manhunt that included a $100,000 reward for information leading to his capture. He is accused of killing his twin sisters, a 79-year-old aunt and 6-year-old cousin on Thanksgiving Day at a family gathering in Jupiter.

Authorities said Merhige checked into the motel in Dec. 2, using the name "John Baca" and a false Homestead address. He had the same blue 2007 Toyota Camry that had been a key part of the manhunt, but police said it was hidden with a covering at the Keys motel.

U.S. Marshals said Merhige, who had withdrawn $12,000 from bank accounts before the killings, paid for his room in advance in cash. It turned out that the license tag on his car had been registered to a Lexus he owned in 2006. Merhige was on his computer when police made entry to his motel room, according to a Marshals statement.

"I'm elated that the monster is in the cage. We don't have to worry about him killing my wife or coming back for my father-in-law. It doesn't bring my daughter back, but at least this chapter is over," Jim Sitton, the father of 6-year-old victim Makayla Sitton, told The Palm Beach Post on Saturday night.

There was no indication Saturday that Merhige had an attorney. Authorities said he was being taken to the Palm Beach County jail.

Police say Merhige opened fire at a home where 16 relatives had gathered for the holiday in Jupiter, an affluent community about 90 miles north of Miami. He faces four counts of first-degree murder and two counts of attempted first-degree murder in the shootings, which also injured two other people.

Police say Merhige shot and killed his 33-year-old twin sisters, Carla Merhige and Lisa Knight, both of Miami, along with his aunt Raymonde Joseph, 76, and his young cousin. Police said Knight was pregnant.

Authorities have said Merhige carefully planned the killings. Sitton has said Merhige was heard saying after the shootings that he had waited 20 years to kill the relatives.

Merhige sat through three hours of dinner and sing-a-longs around the piano before the shootings, Sitton has said. There were no arguments, warnings or red flags before the rampage, he said.

Police said Merhige was taking numerous medications, including Ativan, used to treat anxiety disorders.

Click here for a video report from MyFoxOrlando.com.