ROSEBURG, Ore. (AP) —
    The gunman who killed nine people at an Oregon community college last week complained in writings he left behind that everyone else was crazy and ranted about not having a girlfriend, a law enforcement official said.
    The mother of shooter Christopher Harper-Mercer, 26, has told investigators that he was struggling with some mental health issues, the official also said Monday. The official is familiar with the investigation but was not authorized to speak publicly because it is ongoing.
    In the writings that spanned a couple of pages, Harper-Mercer seemed to feel like he was very rational while others around him were not, the official said.
    He wrote something to the effect of: "Other people think I'm crazy, but I'm not. I'm the sane one," the official said.
    Harper-Mercer killed nine people and wounded nine others, then killed himself after a shootout with police.
    On Monday, some faculty, staff and students returned to Umpqua Community College for the first time since the shooting, while President Barack Obama announced he will travel to Oregon to visit privately with victims' families.
    Classes do not resume until next week, but some students came to the campus to pick up belongings they left behind when they fled the attack Thursday. Others met with professional groups to work through their trauma and grief.
    A memorial was growing on the driveway leading to Snyder Hall, where Harper-Mercer opened fire.
    "It was hard not to focus on Snyder Hall," student Joel Mitchell said. "When we got back, I think a lot of people were probably ... looking at it, checking it out, seeing what it looked like."
    A group of eight held hands and bowed their heads in prayer in front of the building. Elsewhere, clusters of people chatted at picnic tables.
    In a courtyard near the center of campus, a therapy dog sat on a blanket with its handler. A woman, crouched down, wiped away a tear.
    School officials designated an outdoor amphitheater as a makeshift memorial, open only to staff and students for now. Flowers and balloons were positioned on tables, and markers were available for people to write messages on a banner that says, "UCC Strong."
    "I needed to be here," student Madysen Sanchez said. "I needed to come and see my friends, make sure they're OK."
    At least one student injured in the shooting was among those who returned Monday, college President Rita Cavin said. She did not identify the student.
    Chaplains who had been on campus said they were both helping with and participating in the healing process.
    "I'm going through the grieving process myself because this has touched everyone in the community," chaplain Russell Wilson said. "If you don't know someone that goes here, you know someone that knows someone."
    Meanwhile, Obama announced that he will visit Roseburg on Friday as he opens a four-day trip to the West Coast. No additional details about his visit were immediately available.
    Obama has renewed his call for stricter gun laws following the shooting and has expressed exasperation at the frequency of mass shootings in the U.S.