Your brief question can’t be answered as briefly because every suicide is different. Every family of a person who suicided is different as well.
Finding an alternative cause of death is usually not an indication of mass psychosis. Rather, it is often an attempt to reduce the feelings of sadness or to mitigate feelings of regret or guilt or to make a buffer from blame by others. It’s complicated so let me give you a few examples.
Often, family members and friends feel guilty and upset that they didn’t see signs that the person was so depressed and didn’t somehow prevent the suicide (even though it is highly unlikely that they could have). Often they are overwhelmingly sad to think their loved one was that depressed and desperate. It’s not unusual for them to be angry that the person made the decision to die instead of getting help, that they may have even urged the person to get help. Or they may be angry that the helpers couldn’t help enough. Sometimes they are afraid that others will blame them for not preventing it. Sometimes others do distance from family members because they don’t know what to say or even because they worry that suicide is contagious. If one or more of these issues is occurring, it might seem easier to deal with a murder or a cover-up.
My heart goes out to anyone who has experienced the suicide of a loved family member or friend. It is often very, very difficult to accept that the depth of depression was so huge that even the love and friendship of the people who care was not enough to prevent it.
I wish you well.