Could someone have a subdural hematoma even if he is bleeding from the scalp?

Depends on injury: Head injuries are no laughing matter. If the injury is severe there is always a risk of an acute subdural or epidural hematoma. Even with mild injury the elderly are at risk of a slow bleed or chronic subdural hematoma. Any type of head injury that results in direct force to the head should be assessed by a doctor with a complete neurological exam to rule out potential serious complications.

Yes: A subdural hematoma is caused by a tearing of a bridging vein, often from trauma. A scalp laceration would not exclude the possibility of a subdural hematoma.