Mark agonized over the loss of his loved ones.

He worked countless days/nights on his new invention to time travel.

After thorough research, he determined the 'exact intersection' to stop the 'pandemic.'

Mark arrived at its 'beginning'—searched for, found, and killed 'patient zero.'

He returned to the present …

More people had died than before.

Mark traveled to the past again, over and over, at different days/hours/months.

Each trip caused more devastating consequences.

Until the encounter ...

Mark traveled again to the past and saw himself running up to him while pointing a gun—"This is how it ends!"