"We were a few hours behind him," Zikuski said. "Then we put two and two together quickly."
Anderson was enrolled as a nursing student at the State University of New York at Binghamton, and from Westbury, Long Island.
According to Zikuski, Tercero was also a nursing student there and became romantically involved with Anderson going back to early in the Fall term. In September, Zikuski cited an incident in which Anderson filed a police report over damage to her property and blamed Tercero for it. In the report, Anderson said she was in a relationship with Tercero.
Because Terero paid Anderson for the damage -- which Zikuski said involved car tires -- Anderson decided "she didn't want to pursue" the complaint any further.
Anderson was last seen alive at around 4 a.m. on Thursday.
She was with roommates before she went missing, Zikuski said.
The roommates, he said, alerted cops about "concern for her" and a wellness check was prompted.
On Saturday, authorities ruled Anderson's death a homicide. The circumstances of what led to Anderson's death have not been revealed.
As to why Tercero chose to take a flight to Nicaragua, Zikuski said the ex-boyfriend "has family over there."
Even though Tercero was born in Miami, Florida, Zikuski said, it's unclear if he acquired additional citizenship from Nicaragua.
The issue is critical if Tercero has duel citizenship.
While the U.S. has an extradition treaty with the Republic of Nicaragua, Zikuski said he was informed that if Tercero is also a Nicaraguan citizen "it will be harder."
"There's a chance they may not extradite him," he said.