Rhys Lershe, 44, is accused of climbing into the victims' Westampton Township, New Jersey home through an upstairs bedroom window just after midnight Wednesday.
Once inside, police say he demanded the keys to their 2014 black Kia Optima and beat them up before driving off in the car.
The victims were taken to Cooper University Hospital after managing to call police.
Authorities say charges against Lershe are still pending.
Friends and other neighbors describe Lershe as having aggressive and erratic behavior in recent months. His mother said they have tried to get him help for his mental illness as recently as several weeks ago.
"Turn yourself in, take the punishment. You did it and I can't believe he would hurt two old people," said his mother, Lynn Schultz, before his arrest.
She also said family members recently sought protection against Lershe.
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"We have a restraining order against him...he was very abusive saying he was going to do this or that to his older brother," said Schulz.
Neighbors Curtis Parris and Aaron Greene say they heard screams and let the female victim who sought help inside their home to call 911.
"She was covered in blood, she had a lot of injuries to her face. Her husband was attacked as well," said Parris.
More information on Lershe's arrest will be released on Thursday, according to police.