Amid a homicide investigation into Isak Andic’s death, authorities say his son, Jonathan — who is now at the center of the case — had a strained relationship with him.

Andic, 71, fell to his death in on Dec. 14 in the Montserrat mountains near Barcelona, where he was out on a hike with Jonathan Andic, his eldest son, per local outlets El País and La Vanguardia.

The death was initially considered an accident, and Mango issued a statement to that effect after Andic’s death.

Now, Catalan police have shifted the case’s focus to a homicide investigation, according to several sources close to the investigation, El País reported.

Unspecified investigative sources say Andic and Isak had a poor relationship, the outlet reported. Isak’s partner in his later years, professional golfer Estefanía Knuth, reportedly played a role in the souring of this relationship, per the investigative sources.

PEOPLE was not able to immediately reach Knuth for comments.

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Investigators say on the day of the incident, Jonathan and Isak were returning from a hike when Isak fell 320 feet to his death, per U.K. newspaper The Times.

Now, police allege Jonathan gave accounts of the incident inconsistent with what police found at the scene, El País reported.

Moreover, police say the trek of the popular hike is not a dangerous one, which fueled their suspicions, per the outlet.

The Andic family’s spokesperson told El País they are standing by Jonathan and will continue to cooperate with authorities. They said they are “confident that this process will be concluded as soon as possible and that Jonathan Andic’s innocence will be proven.”