Severson, a 20-year-old from Brandon, Manitoba, scored a goal and had an assist to help the Devils defeat the Ottawa Senators 3-2 in overtime on an emotional night at Canadian Tire Centre.
The win snapped the Devils' four-game losing streak. It also ended the Senators' four-game winning streak.
"Losing in a shootout the past two games isn't fun," said Severson, who has four goals and seven points in his first eight NHL games. "Obviously, you want to win those games. Coming in here, we knew we were going to face a tough test. Ended up going up a goal and they scored a late one to tie it up, but going into overtime, we were confident we could pull out the two points."
A ceremony to honor two Canadian soldiers killed earlier in the week preceded the game.
Cpl. Nathan Cirillo was gunned down while he stood on ceremonial guard Wednesday at Canada's National War Memorial in Ottawa. The gunman then stormed Parliament Hill, a short distance away, where he was killed in an exchange of gunfire with security forces.
Warrant Officer Patrick Vincent was killed in what authorities have called a targeted hit-and-run in St. Jean-sur-Richelieu, Quebec, on Monday.
The pregame ceremony also honored the first responders in the incidents.
The Senators and Devils stood alternately around the center-ice circle before the game. Anthem singer Lyndon Slewidge started "O Canada" before raising the microphone to the crowd, which delivered a loud and moving sing-along of the Canadian national anthem.
"It was definitely a heartfelt ceremony. All the fans singing 'O Canada' like that and getting to experience all that situation," Severson said. "As a player, obviously it's a sad day, but to be on the ice with some of those guys and show our respect as both teams did around center ice, it's definitely a nice touch."
Severson continued his strong start to the season when he scored New Jersey's first goal of the game at 11:29 of the second period. He set up defenseman Marek Zidlicky's power-play goal 5:16 later on a cross-ice pass to give the Devils a 2-1 lead after two periods.
Karlsson was slammed into the boards by Devils forward Tuomo Ruutu. Phillips rushed in and grappled with Ruutu before both players fell to the ice. Each player was given a minor penalty for roughing, and Phillips another for unsportsmanlike conduct.
The Devils tied the game 1-1 at 11:29 of the second on some smooth work by Severson, 20, who was selected by New Jersey in the second round (No. 60) of the 2012 NHL Draft.
Severson stepped up to intercept a Karlsson pass, then burst into the Ottawa zone on the right wing. When he hit the edge of the circle to the left of Lehner, he fired a shot that beat the Senators goalie over the right shoulder.
"Karlsson is obviously a very skilled defenseman. I just kind of tried to read it the best I could. It was a chance I had to take," Severson said. "He's good at not looking where he's passing. He wasn't looking at all over there, and I just tried to read it as quick as I could and jump up there, and fortunately enough, I got the puck.
"I usually do like to pass on those situations, but I just saw the shot was there, and it was a tough one not to take."
Devils coach Peter DeBoer has been impressed by Severson so far.
"Just outstanding. He's got poise, composure. He's a special player," DeBoer said.
The Senators (4-2-0) tied the game 2-2 on the power play at 13:51 of the third period when Bobby Ryan fired home a shot from the slot off a pass from Karlsson. It was the Senators' third power-play goal this season on home ice; they had 16 last season.
Senators left wing Milan Michalek dove to knock the puck away from a Devils defender and it wound up on Karlsson's stick. It was Michalek's second assist of the game.
Ryan said the Senators owed it to Phillips to kill off his penalty after he had stepped in to defend Karlsson.
"You can't fault the effort; it was there," Ryan said. "Especially in the third, I thought we took over the game a little bit and for large portions of it. ... They're going to make you pay. Obviously we have to kill that penalty off for [Phillips] for what he did - it's the right play and it's the right thing for him to do. We've got to find a way to come up with that."
The Senators scored the first goal on the power play at 10:09 of the first period when forward Alex Chiasson skated out of the left-wing corner and beat Devils goalie Cory Schneider with a strong shot between the left post and the goalie.
It was Chiasson's second goal. Michalek, who fed Chiasson in the corner, picked up his first point of the season on the assist.
After the emotional pregame ceremony, the teams played a scoreless first period. The Senators were 29th in the League in shots allowed per game (35.6) entering Saturday, but outshot the Devils 11-7 in the first period.
Michalek had one of the Senators' best chances in the first period when he broke in on the left wing and was fed a pass by Ottawa defenseman Codi Ceci.
Schneider, who made 33 saves, moved to his right to stop Michalek's attempt and stayed strong at the post to turn back another attempt by the Ottawa forward.
Jagr, 42, who has two goals, said he's feeling strong.
"The scoring doesn't show, but I feel the best I've felt in probably the last 10 years," he said. "I don't worry about it. I try to play hard every shift. I think I have more confidence. Hopefully my luck is going to turn the right way and it did today. Even if the scoring is not there, that's OK."