If you find someone died with bowel obstruction could there have been gastrointestinal bleeding?

Possibly. Significant bleeding with bowel obstruction is not common. If the obstruction was from a cancer bleeding is perhaps more likely but in general this is not a big issue. There can certainly be bleeding associated with surgery for bowel obstruction.
MAYBE. Bowel obstruction most commonly leads to bowel perforation that then causes peritonitis ( infection of abdominal cavity) which then leads to sepsis (overwhelming infection). This is a life threatening situation. But of course if there is blood vessel involved, for example a very vascular tumor causing the obstruction, yes there might be bleeding.