April Bever, her husband David and their three young children died of “multiple sharp force injuries,” an Oklahoma State Medical Examiner’s Office spokeswoman confirmed to PEOPLE.
The Bevers were found stabbed to death inside their Broken Arrow, Oklahoma, home late last Wednesday evening after one of their sons, who later died, called 911 to report that his older brothers were attacking him.
Police arrested Robert Bever, 18, and his 16-year-old brother, who is not being identified by PEOPLE at this time because he is a minor, just an hour after the call was made.
The two brothers had already run away from the home by then, but a K-9 officer was able to track them down. They were arrested on suspicion of murder and are scheduled to be arraigned on Aug. 3.
Altogether, nine people lived at the home – two parents and seven children, four boys and three girls. Both parents, David, 52, and April, 44, were killed, as were two of the boys, ages 12 and 7, and one of the girls, age 5. The victims were all found in different areas of the home.
A 13-year-old girl suffered critical injuries but has since undergone surgery and is expected to recover. Another 2-year-old girl was found in the home unharmed.
Police recovered multiple weapons used in the killings from the home, including various knives and a hatchet.
Robert has allegedly given a full confession to police, with authorities saying that he showed no remorse as he admitted to stabbing his mother, father and three younger siblings to death.
Authorities said that Bever claimed the murders were “just the beginning” of a series of killings planned outside the family. The extent of these plans remains unclear.
His 16-year-old brother will be charged as an adult when he is arraigned, according to the Tulsa County District Attorney’s Office.
Both brothers were booked into Tulsa County Jail Friday on five counts of murder.
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