The suspect was identified as Attah Ullah, 23, CNN reported. Police did not say whether investigators believe he was the person who shot Malala Yousufzi Oct. 9 or whether he was involved in organizing the attack.
Ullah's mother, fiancee and brother were arrested and charged with aiding him.
The Taliban have taken responsibility for the shooting and said they plan to kill Malala if she recovers. She is currently in a hospital in Birmingham, England, and is still unable to speak.
Malala, a practicing Christian from a Christian family, has advocated for a secular government in Pakistan. The Taliban said that justified her execution.
Also Wednesday, the parents of a 17-year-old girl said she received a threatening phone call two days after Malala was shot, The Guardian reported. Reyatullah Khan and his wife have been involved in efforts to get more educational opportunity for women, and their daughter has joined them in their work.
"The Taliban have kidnapped me and tortured me in the past for promoting women's development, but now they are threatening the entire family," Reyatullah Khan said.
Khan said someone painted a red cross on his gate about two weeks before Malala was shot, and it reappeared every time it was painted over.