EVERETT — For five days, authorities couldn’t figure out how an Everett man suffered injuries that eventually led to his death.

Early Saturday morning, Aug. 8, a resident in the Silver Lake neighborhood called 911, saying they heard someone groaning and crying nearby. A Snohomish County sheriff’s deputy and medics with South County Fire and Rescue found Mark Allan Davis, 46, on the ground in the 3100 block of 110th Street SE, just outside the city. They transported him to Providence Regional Medical Center Everett.

Initially, no foul play was suspected. First responders figured Davis had fallen forward. Perhaps he tripped over a curb or a manhole cover. It was dark outside, and no one reported eye witnesses or obvious evidence at the scene to suggest otherwise.

At the hospital, Davis’ injuries became more apparent. Photos shared with The Daily Herald show that he had two black eyes and scrapes on his arms and legs. He suffered severe head trauma that required extensive surgery. The likelihood of recovery appeared slim.

According to his sister, Donna Schaap, health care staff said that it looked like someone had attacked Davis. The case was referred to the sheriff’s Major Crimes Unit as a possible assault.

Schaap drove from her home in Iowa as soon as she learned Davis was in the hospital. Her adrenaline spiked, she said, and she went 48 hours without sleep. On the way, she called the sheriff’s office in search of answers. She found few, she said.

Family members took Davis off life support on Wednesday, Aug. 12. After an autopsy the next day, the Snohomish County Medical Examiner’s Office determined he likely had been hit by a vehicle and died from blunt force head injuries.

Since the autopsy, the sheriff’s Collisions Investigation Unit has been on the case, often working more than 10 hours a day, sheriff’s spokesperson Courtney O’Keefe said. They’ve found evidence a collision occurred and have collected surveillance video from nearby residents and businesses, O’Keefe said.

Detectives believe the involved vehicle received damage to the front of the driver’s side. They’re asking anyone who may have seen a vehicle that recently sustained such damage to call 911 or the Sheriff’s Office tip line at 425-388-3845. Anyone else who has information about the incident, or who saw Davis walking the night he was hit, is also asked to contact the Sheriff’s Office. Davis was wearing tan pants and a hoodie at the time.

Schaap expressed frustration that authorities didn’t put the pieces together sooner. She questioned why first responders thought Davis had only fallen when he was found with his shoes off, a potential sign he was hit by a larger impact. She put on the hat of investigator herself, going to the scene and talking to neighbors about what happened. When detectives with the Collisions Investigation Unit arrived, Schaap said she introduced herself and stayed for nearly three hours as they investigated.

They were cordial and professional, she said, but she wasn’t going anywhere.

“In my head, I’m not leaving,” Schaap said. “I don’t care how nice you are at this point, you’re going to take care of my brother and I’m going to make sure it happens.”

She said she wants to see justice for her brother, and closure for her family.

O’Keefe said finding the driver might be difficult.

“Without any witnesses, we’re counting on someone from the community coming forward, the driver to come forward or to capture (evidence) on surrounding surveillance,” she said.

According to an obituary published in The Daily Herald, Davis grew up in South Carolina and graduated from Seattle Central College with a degree in web and multimedia management. He worked on web development and IT for Washington’s alcohol and drug 24-hour hotline for eight years and as a chemical dependency professional for Schick Shadel Hospital and Seattle Counseling Services.

At times, Davis dealt with homelessness and an addiction to drugs. On his down days, he was soft-hearted, Schaap said.

“Even when he was homeless and had nothing, he still would’ve helped anyone that he could,” she said.

When she had surgery, for example, her brother took time off work to care for her and her children. He stayed at the hospital and held her hand, even when she wasn’t awake.

More recently, Davis did freelance work in web design and started a lawn care business. During her recent trip to Washington, Schaap said, she visited one of Davis’ customers in Everett, who also had become a friend.

“This is like magazine-quality stuff for what their yard looks like,” she said. “I was absolutely floored because I didn’t realize how talented Mark was in that way.”

Davis also loved animals. Family members are asking that in lieu of flowers, donations be made to the Everett Animal Shelter or another local shelter.

Zachariah Bryan: 425-339-3431; zbryan@heraldnet.com. Twitter: @zachariahtb.