According to a police document released to ESPN, Walton is accused of pushing the woman into a wall and punching her several times in her face and head. Walton is currently being booked into Broward County jail.
Walton's bond was set at $10,000 on Wednesday morning.
The officer called to the scene observed swelling to the woman's left eye. The woman is five weeks pregnant, and Walton is the father. She told officers that she had told Walton about the pregnancy on Sunday. In the audio of the 911 call that was released, the woman says her 2-year-old daughter was in the home at the time of the alleged assault.
The alleged aggravated battery occurred at 4:15 a.m. Tuesday in Davie, Florida, after an argument.
A message to Walton's agent for a response was not immediately returned.
Walton, 22, was through two games of a four-game league suspension for violating the NFL conduct and substance abuse policy relating to his three offseason arrests between January and March. He was released by the Cincinnati Bengals after these arrests, and the Dolphins signed him in May.
The Dolphins initially expected Walton back after he served his suspension, but they immediately released him when they said they were made aware of a police matter regarding the second-year player Tuesday morning.
"We hold our players to a high standard and take these matters very seriously. We will have no further comment at this time," general manager Chris Grier said in a statement.
The Dolphins are now likely in the market for a lead running back starting in 2020. Kalen Ballage has assumed that role in Walton's absence with little success, averaging just 1.9 yards per carry. Patrick Laird and Myles Gaskin have received limited reps behind Ballage. The trio, along with De'Lance Turner, will carry the load for the rest of the season.
Walton, a 2018 fourth-round pick out of the University of Miami, leads the Dolphins with 201 rushing yards on a 3.8 yards-per-carry average. He also has 15 receptions for 89 yards. The league allowed Walton to be at the team facility and attend meetings during his suspension without pay.
Walton received six months of non-reporting probation as part of an August plea deal to resolve his three offseason court cases. Walton's probation was later vacated after he met the court's conditions. Walton's attorney, Michael Gottlieb, said in August that his client had his most significant charge of felony for carrying a concealed weapon from his March arrest reduced to a second-degree misdemeanor open-carry charge after pleading no contest. Walton was arrested after a car chase with police. The plea deal decreased the maximum length of his jail sentence from five years to 60 days.
Walton also pleaded guilty to resisting arrest and reckless driving and had a misdemeanor marijuana charge dismissed from that March arrest. As part of the deal, Walton also had a drug charge from a January arrest and a battery charge from a February arrest dismissed. Walton also had to attend driving school after the reckless-driving plea.
"It's an unfortunate situation. We felt like we had to make a move to release him," Dolphins coach Brian Flores said Wednesday. "That's what it is. Unfortunate situation. You never want to see anything like that happen. Tough.
"Character is something we spend a lot of time on. In this case, it didn't work out with Mark. But it's case-by-case. That's the thought process of the staff and the organization."