Authorities in Northern California are asking for help to find the missing 25-year-old son of two Missouri judges who was last seen leaving his apartment in Sacramento early in the morning on New Year's Eve.

The Sacramento Police Department said that Alexander Holden was last seen around 2:30 a.m. on Tuesday in the downtown Sacramento area.

"Holden’s disappearance is uncharacteristic and family is concerned for his welfare," police said.

FBI SEARCHES IDAHO HOME IN CASE OF 'CULT' COUPLE, 2 MISSING CHILDREN

Holden's girlfriend, Kennedi Perri, said she last saw him shortly before 2:30 a.m. on I Street near 22nd Street as he was leaving their apartment

The 25-year-old "went out with some of his friends, just gotten back from the bar,” Perri told Fox 40. “I had to be up early, so he did wake me up. So we had some conversation.”

Holden told Perri he was headed for a walk to a friend's house and would spend the night there, she said Friday. Perri believes his cellphone died as he was walking toward the Sacramento Northern Bikeway trail.

“He’s a long-distance marathon runner so he has done that trail before and he used to live in Natomas, so it all kind of connects,” Perri told Fox 40.

Alex Holden's Instagram includes photos of him at various running events, including several marathons.

Alex's father, Greene County Judge Calvin Holden, told the Springfield News-Leader his son worked for Amazon, has lived in Sacramento for about two years, and "has no history of disappearing." His father and mother, Associate Judge Margaret Palmietto, cut short their vacation in Australia to head to Sacramento to search for their son.

"Our hearts are with the friends and family of Alex Holden. We have reached out to his family and offered our support, and we hope that he returns home safely," an Amazon spokesperson told Fox News.

Calvin Holden told Fox 40 on Saturday after arriving in Sacramento "it's been hard" and they are "hoping every day he comes home."

"We do know that he’s not in the hospital, he’s not in the jails, he’s not deceased that they know of because nobody’s been shown up," his father said.

BODY IDENTIFIED AS MISSING ALABAMA WOMAN WHO SENT WORRIED TEXT AFTER LEAVING BAR WITH 2 MEN

On Saturday, around a dozen friends and co-workers met at Sutter's Fort Historic Park in Sacramento to post up flyers and canvass the city looking for Holden.

One of Alex's friends, Aumad Malik, told Fox 40 he thought the 25-year-old was coming over to his house after doing it "a hundred times."

"It’s just this time is worrying because he didn’t make it there," Malik said. "We need to find out where he is. We need to find out where he is and what happened."

Malik described Alex as a "really, really nice guy" who is "super trusting."

"He makes friends everywhere he goes so we’re really hoping that someone may have seen him or talked to him that night because he’s the type to make conversation wherever he’s at," Malik told Fox 40.

CLICK HERE FOR THE FOX NEWS APP

The Sacramento Police Department said that Alex Holden is described as 6-feet, 1-inch tall, has green eyes, weighs about 190 pounds and was last known to be wearing the tan pullover and Birkenstock sandals.

Anyone with information is asked to contact the Sacramento police.