Investigators believe that Ewell pretended to be a utility repairman to get into the home of Leamond Turnage, 69, and his wife Robyn, 57.
The deceased couple was found gagged and bound Friday afternoon in their home on the 4100 block of West 142nd Street. Police believe that the couple was likely killed Thursday afternoon.
Authorities said Ewell was caught on surveillance footage trying to use the couple's stolen ATM card at a gas station on the day of the killings.
The couple's relatives alerted authorities when they weren't able to contact them. The Turnages had just returned home from Florida after witnessing the birth of their granddaughter.
Investigators said they were not surprised that Ewell remained in the Hawthorne area to use the stolen debit card.
"He certainly left a trail for us to follow and we consider ourselves fortunate in that regard, but obviously unfortunate in the sense that he was still able to murder two people before we were able to find him," said Lt. Gary Tomatani.
"In less than 24 hours after we were notified, this team was able to walk into a cold who-done-it double murder, identify a suspect and get him in custody and take him off the streets," said Los Angeles County Sheriff's Department Lt. Dale Coleman.
Authorities think there may be a connection between the murders and a home-invasion robbery that happened in September in the same area, just five blocks away from the Turnages' home.
A man in his 80s died of a heart attack after the robber assaulted him and tied him up. A $10,000 reward is being offered for information leading to an arrest.
Surveillance footage shot from a home across the street from last month's invasion shows a tall, slender man leaving the home carrying a briefcase. Deputies believe that he could be the man responsible for that attack.