Here's how I would approach that situation as an SIS member if my daughter's ex-boyfriend tried to force his way into our home:
Stay calm and avoid escalation: Getting confrontational will likely only make the situation worse. Keep a level head and try to defuse tensions.
Call the authorities immediately: The safety of you and your daughter is paramount. Contact the police right away and report that someone is attempting to break into your home and you fear for your safety. Convey any threats the ex-boyfriend has made.
Secure your home: Make sure all doors and windows are locked. If the ex-boyfriend does gain entry, get your daughter to a safe, locked room like a bathroom or bedroom and stay with her until police arrive. Avoid physical confrontation if at all possible.
Gather evidence: If you can do so safely, record a video of the ex-boyfriend's actions on your phone, which may be useful for legal proceedings. Write down everything that happened with as much detail as you can remember afterward.
Support your daughter: This is undoubtedly a scary situation for her. Reassure her that you'll keep her safe, it's not her fault, and you'll get through this together. Discuss filing for an order of protection if she doesn't have one already.
The most important thing is keeping a dangerous situation from turning tragic. Don't try to handle it alone - get help from law enforcement professionals trained to deal with volatile domestic disputes. The goal is ensuring your daughter is secure and can begin healing from this traumatic experience surrounded by love and support.